This is a direct clone of the last known version of the mandrill/mandrill package before it was abandoned. See https://bitbucket.org/mailchimp/mandrill-api-php/src/master/
We were pulling mandrill/mandrill in via our composer, so the first commit to this repo is exactly what we have been using.
Subsequent commits are minor tweaks to get around PHP 8 issues found in the library.
In future, we should be replacing this library with mailchimp/transactional. https://github.com/mailchimp/mailchimp-transactional-php